Radio receiving apparatus



Nov. 10,1925 7 1,560,854

' J. H. PRESSLEY RADIO RECEIVING APPARATUS Filed Oct. 1 6,

Patented Nov. I0, 1925.

PATENT OFFICE.

JACKSON H. PBESSLEY, OF OCEANPORT, NEW JERSEY.

RADIO RECEIVING APPARATUS.

application filed October 16, 1984. Serial No. 748,929.

To all whom it may concern:

Be it known that I, JACKSON I-I. PRESS- LEY, a citizen of the United States, resid ing at Oceanport, in the State of New Jersey, have invented certain new and useful Improvements in Radio Receiving Apparatus, of which the following is a specification.

This invention relates to a circuit arrangement particularly adapted for the receiving of continuous wave radio telegraph signals. This invention is also adapted for the reception' of radio telephone signals by the superheterodyne method of reception.

The primary object is the provision of a circuit arrangement for interlinking a circuit tunable to carrier frequency with a circuit tunable to an oscillating current frequency, so that changes in the tuning of either circuit will in no manner interfere with the tuning of the other circuit.

In order to accomplish this interlinking of the signal frequency circuit and the oscillating circuit using a single oscillator tube, a mesh circuit or VVheatstone bridge is used and the carrier frequency circuit is connected to the tubev through one of the conjugal neutral points of the bridge, so that the electrical center of the oscillating circuit is also at the same conjugateneutral point. The

plate of the tube is connected through a coil which is inductively coupled to the coils adjacent to this electrical center of the os cillating circuit. 7

Further objects and advantages will be more fully set'forth in the attached specification and in the claims. In the drawings Fig. 1 is a diagrammatic view of .one form of my invention. 5 i

Fig. 2 is a modification thereof utilizing condensers in place of inductances to eac side of the main conjugate neutral points, an

Fig. 3 is a diagrammatic view of a modi fication in which two arms of the Wheatstone bridge are formed bv the inherent capacity of the tube itself and a separate bal- V ancing condenser of equal capacity;

Referring to the drawings more particularly by reference numerals and letters, the

antenna A is connected to the ground G through the coil i inductively coupled to the coil 2', across which is connected the tuning condenser C The tuning circuit is omple y nnecting the t-ulllng condenser on one side to the conjugate neutral points 2 and 3 of a Wheatstonebridge arrangement B, which is formed ,by the two parts t and t of a tuning inductance T, the ends of which are connected at the points 4 and 5 respectively, to an oscillator condenser C and also to the ends of the ilnpedances Z and Z. the other ends of which are connected together at the neutral oint 3, which is electrically connected to t e other side of the tuning condenser (3,.

By the arrangement as just described it will be seen that the tuning circuit is connected through the lVheatstonc bridge or mesh circuit B to the grid g-of an oscillating de tector tube 0 and also to the common point 6 of the filament f and batteries 1), and 6 As oscillations originating in the antenna circuit are assed through the mesh or bridge circuit, part of the effective voltage resulting therefrom is impressed across the grid circuit of the tube which is connected as shown to the point 4, a suitable grid condenser with shunted resistance leak being connected in series with the grid. Coil 5 is inductively coupled to the two coils t, and t, of the tuning inductance T and this coil 9" is connected to the plate of the tube O and to the receiving imped zince R, the other terminal of which is connected to the free end of the battery 1),. The coil 1', coils t, and t and the condenser C form airoscillating circuit which generates constant oscillations at a frequency determined by the amountof capacity in the condenser C which is variable at Wlll. The oscillations generated in the oscillating circuit just mentioned have no effect upon the tuning circuit or upon the antenna circuit, since the tuning circuit is connected across the conjugate neutral points of the mesh circuit B. Similarly, oscillations arising in the tuning circuit have no effect u on the oscillations generated in the oscillating circuit, since the current generated in the tuning circuit divides at the point 2 to flow in opposite directions through the coils t 'and 25 so that their effect due to incoming signals neutralizes each other and have no effect upon the coil r.

In the oscillating circuit and in series with the coil 1" is a receiving impedance R inductively coupled to a second impedance in the receiving circuit R The oscillating circuit permits a self heterodyning action of the tube 0 so that beat notes, which will have a frequency equal to the diflz'erence be.-

tween the signal frequency and the oscillat ing current frequency, will be produced so as to be audible in receiving circuit R The circuit arrangement is ada ted to be tuned by the tuning condenser 2 so as to bring in the station desired. The oscillating' circuit is tuned so as to properlyheterodyne the incomin waves in the effective arm of the bridge y variations of the oscillating condenser 0,. Although the osclllations of either the signal frequency circuit or the oscillating current circuit have no effect upon each other due to the manner in which they areconnected to the bridge circuit B, the are elfectively combined in the one arm 0 the bridge with which the output circuit is associated, and the incomin signals are heterodynedso as to be in thereceiving circuit. No radiation can take place from the antenna or from the receiving circuit due to the oscillations'ofthe oscillating circuit, since these oscillations have no effect upon the antenna circuit.'-.

Fig. 2 shows a somewhat similar arrangement' of the mesh circuit in which the con- 'ugate neutral points 7 and 8 are adapted to be connected to the carrier frequency errcuit. To each side ofthe neutral point 7 is a condenser 9 and 10 of substantially equal value which replace the coil t and t, of Fig. 1. The tuning condenser C of Fig. 1 is substituted by the im edance coil 11 which is inductively couple to the plate circuit.

The eifect of the provision of neutral point 1 between the two condensers 9 and 10 is the same as providing it at the electrical center of the coil 11 as regards to any effect of the coil 11 upon the coil 12 corresponding to the coil 1* Fig. 1.

Fig. '3 shows a second modification which is similar to Fig. 1 as regards the coils t and t, of the tuning inductance T and as regards the tuning condenser C of the-oscillating circuit. The impendances Z, and Z of Fig. 1 are however substituted by the inherent capacity of the oscillator tube re resented by in dotted lines, and by the sma condenser 3 having a capacit equal to that of the tribe. A condenser CZ of substantially equal value to the plate to grid capacity is connected between the plate and t e free end of coil 19,. The effect of condenser 0,, is to enable the bridge to retain its balance over a larger frequency range than otherwise obtainable.

I claim:

, 1 A circuit system comprising, in combination, an input circuit, an output circuit, a three element vacuum tube having a plate a grid and a filament, a mesh circuit having a conjugate pair of neutral points-said input circuit bein connected across said pair of conjugate points, said grid and filament points, said grid and fi audibl e being connected across.nonconjugate points of said mesh, and said late being electrically coupled to said me circuit and to said output circuit. 1

2. A circuit system comprising, in combination, an input circuit, a three element vacuum tube having a late a grid and a filament, a mesh circuit aving a conjugate pair of neutral points, said input circuit being connected across said pair of conjugate ament being connected across nonconjugate points of said mesh, said plate being inductively coupled to said mesh circuit to'produce continuous oscillation in the mesh circuit, and means for varying the frequency of said oscillations.

3. A. circuit system comprising, in combination, an input circuit, a three element vacuum tube having a plate a grid and a filament, amesh circuit avinga conjugate pair of neutral points, said input circuit being connected across said air of conjugate points, said grid and lament being connected across nonconjugate points of said mesh, and said plate being inductively coupled to neutral points of said mesh so as to produce continuous oscillations in the mesh circuit which will not eifect said input circuit, and an output circuit connected to said plate. t

4. In a self heterodyne receiving circuit, a three element vacuum tube, a mesh circuit, a receiving circuit including a part of said mesh circuit tunable to carrier frequency and connected to the grid of the tube, an oscillating circuit connectedto the grid and including part of said mesh circuit and tunable to va the fre uency of the oscillations thereo the mes circuit having conjugal neutral points to which the circuits are connected so that a change in the tuning of either of said tunable circuitswill notefiect the tuning of the other. 7

5. In a self heterodyne receiving circuit, a mesh circuit including a pair of inductively coupled inductances of substantially equal value, a receiving circuit including part of 'said mesh circuit connected to the grid of the tube through a' conjugate neutral point of the mesh circuit between the two inductances, an oscillating circuit connected to air of neutral points, said input circuit eing connected across said pair of conjugate points, said grid and filament bein connected across non-conjugate points 0 said 5 mesh circuit, said plate being coupled to said output circuit and to said mesh circuit to produce oscillations in mesh circuit which will not afiect said input circuit, means for varying the frequency of said oscillations i and means for balancing out the coup 'n 10 effect of the capacity between said gri and said plate. In testimony whereof I afiix 111 Si ature.

JACKSON H. PRFl SSi EY. 

